Key figures in both parties put increased pressure yesterday on President Clinton to resolve the legal and personal charges he faces, warning that a lengthy delay could damage foreign relations and produce gridlock on Capitol Hill.

Sen. Daniel Patrick Moynihan (D-N.Y.) voiced a growing sentiment when he said in an interview, "The president is the only one who knows the truth of what happened and he should make it clear immediately."

Sen. Richard G. Lugar (R-Ind.), attending a conference in California of Asian and U.S. leaders, said: "If the president is prepared to testify to the full truth and his lawyers permit it, he should do it at once. . . . With the problems we face from Iraq to Asia, an alert, active president is needed."

Their comments and similar views came a day after Clinton's former White House chief of staff, Leon E. Panetta, told the San Jose Mercury-News, "This thing has got to be resolved quickly. He should do it before the State of the Union address," scheduled for Tuesday night.

"If he doesn't," Panetta said, "people will continue to raise more questions. You can't sidestep an issue this big."

Rep. Charles B. Rangel (D-N.Y.) said on CNN's "Evans & Novak" show yesterday, "The president should deal with this in a more candid and forward manner," either before the State of the Union address or soon thereafter.

Rep. Lee H. Hamilton (D-Ind.), like Lugar a longtime leader on foreign policy issues, said, "I hope against hope we won't have a crisis" in the world while the charges of an affair with a White House intern and her tape-recorded statement that Clinton asked her to cover it up are unresolved. "It's discouraging that we have these kinds of diversions."

A Democratic senator who declined to be identified expressed frustration. "I don't see why we are more than four or five days from getting this settled," he said. "If what is alleged is true, he should quietly depart. If it's not true, he should blow up Mr. Starr's building," referring to the offices of Whitewater independent counsel Kenneth W. Starr, "and then get some psychiatric help for Ms. [Monica] Lewinsky," the former intern who claims on FBI tapes to have had an affair with Clinton.

But others said that hard as it may be for the country, they do not expect Clinton to move quickly to resolve the unanswered questions. A longtime Arkansas associate of the president's called the situation "very saddening," but said Clinton is "the eternal optimist. He probably sees light at the end of the tunnel. I don't. I think he's taken a hit and will suffer terribly over the next few months. But his attorneys must be telling him, 'Let's take our time and find out as much as we can about what these people have' "

Lugar said, "I have been amazed" at how Clinton has been able to focus on world problems during past scandals involving Cabinet and White House officials. "Even on days when people all around him were being subpoenaed, he remains cheerful and buoyant. His ability to function during all this has been remarkable. I just don't know when the critical mass becomes too much."

A senior Democratic figure in Washington who spoke with the president yesterday said Clinton blamed his predicament on "the bad people who are after him." The official said his impression is that Clinton "has the gall to brazen it out. He'll get into a swearing contest with this gal. He doesn't worry about his pride."

Several Democrats echoed Panetta's worry that a protracted legal battle between the White House and Starr's investigators could damage prospects for action in the session of Congress beginning Tuesday. "You're dealing with a Congress that is likely to move against him in the Judiciary Committee," Panetta said, referring to possible impeachment proceedings in that House panel. "And unless he's got a clear resolution of this matter, Congress itself is going to be paralyzed."

Other Democrats argued, however, that Republicans, who largely have withheld fire since the scandal story broke last Tuesday night, have a motive for their reticence. "If there's one thing they don't want," a Democratic senator said, "it's Al Gore sitting in the White House before 2000. The president has that going for him. But in the end, this can't be manipulated. He's going to have to face it."